Water-dilutable stone impact protection paint and compensation paint, their use and process for their production

ABSTRACT

Disclosed is the preparation of a water-dilutable stone impact protection and of a compensation paint and its use and processes for their production, especially in the automobile industry. The water-dilutable stone impact protection paint contains 20 to 60 wt % binder and 2 to 10 wt % pigments and possibly uncoagulated overspray of water-soluble base paints and the compensation paint contains 40 to 80 wt % binder.

[0001] The invention relates to the creation of a water-dilutable stonechip protection paint and compensation paint, to their use and toprocesses for producing the same, especially in the motorcar industry.

[0002] A basical problem in the lacquering of surfaces, in particular ofmotorcar bodies, is the stone chip resistance of the overall lacquering.The stone impact resistance of conventional paints substantially dependson the primer surfacer layer located on the electrocoat layer and havinga thickness of about 30 to 40 μm which, on the one hand, equalizes therough surface of the crude up minor surface inequalities and mainlyoffers protection motorcar shell to allow subsequent coating with acovering lacquer, fills against mechanical attacks (stone chipprotection function).

[0003] A conventional motorcar lacquer coating according to theso-called “base coat/clear coat process” consists, for example, of atotal of four layers. These four layers are applied one after the otherin separate lacquering devices. The first layer, directly located on thecar sheet metal, is the electrocoat layer which is applied byelectro-dipcoating—mainly cathodic dipcoating (CDC)—for protectionagainst corrosion. The nature of the electro-dipcoating prevents theformation of overspray.

[0004] The second layer, located on the electrocoat layer and having alayer thickness of about 30 to 40 μm is the so-called primar surfacerlayer which, on the one hand, equalizes the rough surface of the crudemotorcar shell to allow subsequent coating with a covering lacquer,levels minor surface inequalities and mainly offers protection againstmechanical attacks (stone chip protection function). This layer issubstantially produced by electrostatic application of a baking enamel,for example, with electrostatic high rotation bell, followed by bakingat temperatures of above 160° C.

[0005] The third, layer located on the primar surfacer layer, is thebase coat layer which imparts to the motorcar body the desired color byvirtue of adequate pigments. The water soluble base coat is applied byconventional spray methods.

[0006] The fourth and uppermost layer, located on the base coat layer,is the clear coat layer which, analogous to the base coat layer, isapplied by conventional spray methods and, on the one hand, imparts thedesired lustre and, on the other hand, protects the base coat againstenvironmental factors (UV radiation, salt water etc.).

[0007] The object of the invention is to create a stone chip protectionpaint which meets the requirements of the tests prescribed by themotorcar industry and, at the same time, takes over the function of theconventional primar surfacer or the function of the conventional and theconventional base coat layer.

[0008] This problem is solved by the present invention by providing awater-dilutable stone chip protection paint, containing from 20 to 60%by weight binders and from 2 to 10% by weight pigments, and by awater-dilutable compensation paint, containing from 40 to 80% by weightbinders. The compensation paint may additionally contain up to 20% byweight pigments.

[0009] Pigments, as defined by the present invention, include inorganicor organic multicoloured or achromatic colorants that are practicallyinsoluble in the medium in which they are applied, such as described,for example, in “Glasurit-Handbuch Lacke und Farben”, 11th edition,published by Curt R. Vincentz, Hannover 1984, p. 97-108, i.e. carbonblack titanium dioxide, effect pigments, such as aluminum bronzes, micapigments and the like.

[0010] A binder as defined here and in the following includes substanceswhich bond together similar or different kinds of substances, inparticular the non-volatile component of a lacquer without pigment andfiller, but including plasticizers, drying agents and other non-volatileadditives, preferably the water compatible film-forming resins, such aspolyester, polyurethane and acrylate resins and the like, as described,for example, in “Glasurit-Handbuch Lacke und Farben”, loc. cit. p. 19-96or in H. Wagner, H. F. Sarx “Lackkunstharz e”, Carl Hanser Verlag Munich1972.

[0011] In a further embodiment of the invention, the ratio of binders topigments in the water-dilutable stone chip protection paint is between5:1 and 12:1 or between 10:1 and 15:1 in the case of the water-dilutablecompensation paint.

[0012] Inasmuch as the water-dilutable stone chip protection paint orthe compensation paint contains pigments, the latter can be an effectpigment, in particular an aluminium bronze.

[0013] In a preferred embodiment of the invention, the binder of thestone chip protection paint or the compensation paint is a watercompatible blocked isocyanate, a polyurethane resin, a polyester resinand/or melamine resin.

[0014] In a further embodiment of the present invention, this polyesterresin has an average molecular weight of from 5,000 to 10,000, exhibitsan adequate number of carboxyl groups which after neutralisation withbases impart to the polyester resin sufficient water-dilutableproperties; and contains functional groups, in particular hydroxylgroups by virtue of which the polyester resin is made cross-linkable.

[0015] The polyester resin can have a OH number of from 20 to 80, inparticular from 30 to 60 and an acid number between 10 and 50, inparticular from 15 to 35.

[0016] Its glass transition temperature (Tg) may be between −20 and +30.

[0017] In a further embodiment of the invention, the polyester is inparticular a polycondensation product of a diol and a dicarboxylic acidin the presence of a component containing more than 2 functional groups.

[0018] The diol is selected from the group consisting of 1,6-hexanediol,neopentyl glycol, 1,4-dimethylolcyclohexane, hydroxypivalic acidneopentyl glycol ester (HPN), perhydrogenated bisphenol A,trimethylolpropane and trimethylolpropane monoallyl ether.

[0019] The dicarboxylic acid is selected from the group consisting ofadipic acid, phthalic acid, isophthalic acid, hexahydrophthalic acid,tetrahydrophthalic acid or their possible anhydrides, in particular fromthe group of dimeric fatty acids.

[0020] The component containing more than 2 functional groups may be atriol, a tricarboxylic acid, a monohydroxydicarboxylic acid, inparticular a dihydroxymonocarboxylic acid, preferably trimellithic acid,trimethylolpropane and dimethylolpropionic acid.

[0021] The best properties can be achieved with binders exhibitingelastomeric characteristics after baking. These can be specificpolyurethanes in which, due to their segmented structure, a specificsequence of soft and hard segments is observed. Preferred binders aresoft polyester resins having a high molecular weight and a highhydroxy-functionality, obtained by polycondensation of dimeric fattyacids and polyalcohols, preferably diols, their crosslinked sites beingproduced by trifunctional (hydroxy)carboxylic acids. These polyesterresins are also used with blocked polyisocyanates or melamine resins ascross-linking agents.

[0022] Furthermore, the water-dilutable stone impact-protection paint orcompensation paint can additionally contain organic solvents andadditives.

[0023] The term solvent as used hereinafter includes those organicsubstances which can dissolve other substances in a physical manner,such as, e.g., lower alcohols, glycol ether, lower ketones, inparticular organic solvents which are substantially miscible with water,such as butanol, isopropanol, methylethyl ketone and many others, suchas described for example, in “Glasurit-Handbuch Lacke und Farben”, loc.cit. pages 117-138.

[0024] Additives are defined as substances that are added in smallamounts to other substances, in particular liquid substances, to changetheir properties in a desired manner or to facilitate their processing.Additives include gloss products, wetting agents, drying agentssedimentation inhibitors, antifloating agents, film-inhibiting agents,leveling agents, release agents, lubricants as well as UV absorbers,biocides, plasticizers, antistats, stabilizers, antioxidants,antiozonants, fillers, viscosity control agents, aging inhibitors,detergents, dispersing agents, defoamers, setting accelerators,solidification retarders or drying agents, as described, e.g., in“Glasurit-Handbuch Lacke und Farben”, loc. cit. p. 113-117.

[0025] The invention also relates to the use of a water-dilutable stonechip protection paint for coating motorcar bodies having an electro-dipprimer coat, a second so-called primar surfacer layer, a third layercomprising a water-soluble base coat and a covering layer of clear coat,the primar surfacer layer being replaced by a stone chip protectionlayer consisting of the stone chip protection paint and having athickness of from 10 to 20 μm.

[0026] In a further embodiment of the present invention, thewater-dilutable stone chip protection paint is used for coating motorcarbodies having an electro-dip primer coat, a stone chip protection layerconsisting of the stone chip protection paint having a thickness of from10 to 20 μm and a covering layer of clear coat.

[0027] The water-dilutable compensation paint of the present inventionis used in mixture with a commercial base coat for coating motorcarbodies having an electro-dip primer coat, a second so-called primarsurfacer layer, a third layer consisting of a water-soluble base coatand a covering layer of clear coat, the primar surfacer layer beingreplaced by a mixture of water-dilutable compensation paint andcommercial base coat having a thickness of from 10 to 20 μm.

[0028] According to another embodiment of the invention, thewater-dilutable compensation paint is used in mixture with a commercialbase coat for coating motorcar bodies having an electro-dip primer coat,a layer comprising the mixture of water-dilutable compensation paint andcommercial base coat having a thickness of from 10 to 20 μm and acovering layer of clear coat.

[0029] Thus, the compensation paint serves for conditioning the basecoat, i.e. it imparts to a conventional base coat stone chip protectionand primar surfacer properties so that the base coat either replacesonly the primar surfacer layer (four layer-structure) or the primarsurfacer layer and the base coat layer simultaneously (threelayer-structure).

[0030] This conditioning adapts in particular the adhesion of the stonechip protection layer in such a manner that if a strong mechanical loadfrom an outward source acts on the overall lacquering, which upon usinga three layer-coating (i.e. without primar surfacer layer) without thelayer of the present invention, would lead to a chipping off of theelectrocoat layer, the adherence to the electrocoat layer is controlledto such an extent that, on the one hand, the stone chip protection layeris released from the electrocoat layer, but does not pull the latterfrom the motorcar sheet metal and, on the other hand, the chipping offsare as little as possible. The latter can be achieved by additives whichspecifically increase the rebound resilience of the stone chipprotection paint. Rebound resistance as used herein means the propertyby means of which a mechanical impulse (stone impact) is counterbalancedby an elastic deformation. A damage of the material is inhibitedthereby.

[0031] There are different methods of testing the property ofpredetermined stability of the pertinent layer, namely of said stoneimpact protection paint or of a base coat conditioned by saidcompensation paint, said methods being adapted to the specific field ofapplication, however, all of them aim at reproducing the mechanicalaction as exactly as possible. There are, for example, prescribed testsin the motorcar industry which try to simulate the stone impact by theimpact of a shot (Mercedes-Benz AG, lacquer testing apparatus with shottesting apparatus at temperatures of −20 to +50° C., a shot diameter offrom 2 to 4 mm and a shot speed of from 50 to 300 km/h) or a chisel-liketesting device (Test VDA 621-428 of BMW-AG) on the finished lacqueredsurface at exactly defined temperatures (room temperature and −20° C.)and further exactly defined parameters.

[0032] In a particularly preferred embodiment of the invention, thewater-dilutable stone impact protection paint contains overspray fromwater-soluble base coats, in particular from spraybooth waste water.

[0033] An overspray is the excess of lacquer which during theapplication of the lacquer by spray painting techniques does not hit thearticle being lacquered but misses the target and is discharged togetherwith the exhaust air from the lacquering zone in order to betransferred, for example in a wet wash out step, to the wash out waterof the spraybooths—referred to hereinafter as booth waste water—to washout the lacquer components present in the overspray.

[0034] A big problem generally encountered in lacquering processes isthe waste material, in particular paint sludges. Paint sludges areusually produced when the substantially water-insoluble lacquercomponents are removed from the booth waste water by coagulation toallow the booth waste water, recovered after sedimentation or separationof the paint sludge, to be recycled for reasons of environmentalprotection.

[0035] In view of the high costs of waste disposal, the lacquermanufacturing and the lacquer processing industries are increasinglyinterested in applying new methods to avoid this kind of waste. To thisend, there are basically two possibilities. On the one hand, one istrying to practically inhibit the formation of an overspray right fromthe beginning by applying specific and more sophisticated lacqueringmethods. The latter include flow coating, casting, dipcoating, rollcoating, coil coating, electro-dipcoating or the like. On the otherhand, one is trying to recycle the overspray which is necessarily alwaysformed, for example, when using spray painting techniques. At present,the degree of coating efficiency of this spraying method (air, airlessor air mix atomization etc.) is from 20 to 80%, i.e. only from 20 to 80%of the sprayed lacquer hit the surface of the article being lacquered,the rest accrues as overspray.

[0036] A conventional water-soluble base coat usually consists of

[0037] from 5 to 15% by weight pigments,

[0038] from 10 to 20% by weight binders

[0039] 0 to 20% by weight organic solvents

[0040] 0 to 5% by weight additives

[0041] 40 to 85% by weight water.

[0042] A particularly serious problem is the recycling of base coatoversprays. Since, for logistic reasons, the motorcar bodies in afactory are not sprayed serially with the different colors (i.e. notonly black on mondays, only white on tuesdays and only red bodies onwednesdays etc.) but several color shades within one hour, one alwaysobtains a variable amount of water-soluble base coat overspray ofdifferent colors in the booth waste water. Therefore, the booth wastewater has an unsightly shot color from sludgy brown to dirty gray. Thisexcludes the return of this component to the base coat being coated, asproposed in DE-OS 42 13 671.

[0043] To date, in all motorcar body lacquering plants, theoverspray-containing booth waste waters are converted into a lacquersludge by coagulating agents. In former times, this lacquer sludge wastransported to a waste dump, which is now forbidden by law Therefore,nowadays this coagulate or paint sludge, which still contains about 50%by weight water, is reprocessed, after removal of the main amount ofwater, drying in rotating tubular kilns and grinding to form granulatesor powder, and is reutilized for other purposes. This means in the caseof the granulates, that they are disposed of by the so-called “thermalrecovery”, i.e. incineration of special waste. The energy recoveredthereby does neither compensate the loss of material nor the expenditureof method and capital.

[0044] The recovery of the booth waste water-overspray in the sense of arecycling to the spraying process, i.e. a recovery on a higher level, isonly possible in the processing of water thinnable lacquers. Waterthinnable lacquers are those systems which contain, beside theconventional lacquer components, water-dispersible binders and whichhave water as main solvent. When using water thinnable lacquers in spraycoating techniques, one has the possibility of precipitating theoverspray in the booth waste water in such a manner that coagulationdoes not take place. Thus, the booth waste water becomes a very dilutedwater thinnable lacquer which can be depleted from excess water bysuitable methods and be reutilized as lacquer. Thus, DE-OS 42 13 671describes a process for recovering the overspray from aqueous coatingcompositions during spray coating in water dripping spraybooths by meansof ultrafiltration which allows to concentrate the enriched booth wastewater (retentate) to a solids content of up to 35% by weight. DE-OS 4207 425 describes a process for recovering the lacquer overspray ofaqueous lacquers during spray coating by ultrafiltration and sebsequentelectrophoresis. Further processes for recovering water thinnablelacquer oversprays are described in DE-OS 34 28 300, CH-OS 1656/59,DE-OS 41 33 130 and DE-OS 42 02 539.

[0045] It has also been contemplated to recycle the booth waste wateruntil a water thinnable lacquer concentration is obtained in said boothwaste water which permits the direct use of the latter as thinnablelacquer. JP-PS 49 51 324 teaches to increase the concentration oflacquer in the lacquer-containing precipitate by removal of water fromthe entire booth waste water to such an extent that this precipitate canbe reutilized for color spray painting. However, practical tests showedthat a concentration of thinnable lacquers in booth waste water to asolids concentration of more than 2% by weight results in that theoverspray is no longer completely washed out and the discharged exhaustair contains more overspray than is prescribed by the law (technicalinstructions on air quality control). The solids concentration refers tothe overall amount of non-volatile lacquer components, such as pigments,binders, additives etc., expressed as weight percent, based on the totalcontent of all lacquer components.

[0046] DE-OS 42 13 671 and 41 33 130 teach methods of recovering theoversprays of aqueous coating compositions during spray coating in spraybooths according to which part of the liquid circulating in theultrafiltration cycle is used as aqueous coating composition for spraycoating. This circulating liquid is alway added to the same sprayingcomposition from which overspray it is obtained.

[0047] The overspray comprising aqueous base lacquers for producing astone impact protection layer which dries at from 50 to 90° C. is usedaccording to the invention between the electrocoat layer and the baselacquer layer.

[0048] For the purposes of the invention, the overspray can be recoveredby any conventional method. Its accumulation can be effected, forexample, according to the lacquer recovery methods described in I-Lack61 (1993), p. 425-428 (washer device, recovery wall, recovery belt,Relas lamella-recovery system). The overspray is preferably recovered ina condition allowing its use according to the invention by means of anyprior art wet wash out method. This wet wash out results in anaccumulation of the overspray in the booth waste water.

[0049] With respect to the composition of the individual lacquercomponents, the overspray in the booth waste water has a differentcomposition from the base coat since, for example, the evaporation ofthe volatile organic solvents is quicker and, therefore, escape to theatmosphere together with the exhaust air from the spraybooth.

[0050] The booth waste water normally consists of

[0051] form 0.1 to 1.5% by weight pigments,

[0052] from 0.1 to 2.0% by weight binders,

[0053] from 0 to 2.0% by weight organic solvents,

[0054] from 0 to 0.5% by weight additives and

[0055] from 94 to 99.8% by weight water.

[0056] Booth waste water containing an overspray which consists ofwater-soluble base coats of different colors is preferably used for thepurposes of the invention.

[0057] This booth waste water is preferably used in a water-depletedupgraded form in the light of the invention. This upgrading by waterdepletion can be effected by any separation procedure familiar to theexpert, such as concentration by vaporization, concentration by boilingin vacuo, freezing out, centrifugation or freeze drying. An upgrading ofthe booth waste water is usually conducted by ultrafiltration or acombination of ultrafiltration and electrophoresis (DE-OS 42 97 425).

[0058] This upgraded booth waste water has a solids concentration offrom 10 to 35% by weight. In the upgrading of overspray absorbed inwater, changes in respect of the composition of the concentrate because,for example, preferably water-insoluble and high molecular weightcomponents such as pigments and binders are retained by ultrafiltrationwhile the water soluble and low molecular weight components, such assolvents, melamine resins and neutralizing agents preferably aretransferred to the permeate. The water depletion can also result in achange of the properties of the paint components, such as color shadeand rheology.

[0059] The upgraded booth waste water usually consists of

[0060] from 2 to 12% by weight pigments,

[0061] from 4 to 18% by weight binders,

[0062] from 0 to 5% by weight organic solvents,

[0063] from 0 to 0.8% by weight additives,

[0064] from 64 to 94% by weight water.

[0065] Thus, by virtue of the production of the stone chip protectionpaint of the present invention, a big problem of the spray coatingtechnique according to the “base coat/clear coat” method is solvedbecause all of the overspray accrued in the spray coating of the basecoat layer in the booth waste water can be utilized. This means that itis no longer necessary to coagulate booth waste water and, consequently,paint sludge is not obtained when the base coat layer is applied.

[0066] In addition, this means that both the base coat overspray as wellas the overspray of the stone chip protection paint recovered therefromcan be united in one booth waste water.

[0067] A basical advantage of using booth waste water for producingstone chip protection paint is that the booth waste water may alsocontain different color shades of the water-soluble base coats and can,nevertheless, be reutilized as valuable material.

[0068] A further particular advantage in replacing the conventionalfiller layer by the stone chip protection layer of the present inventionconsists in that the baking of this primar surfacer layer can bedispensed with. The stone chip protection layer of the present inventiondries at a temperature of between 50 and 90° C. and, consequently,necessitates, for example, only a drying or a predrying with infraredradiation. This means a considerable saving of energy and time.Moreover, it is not necessary to apply the stone chip protection layerof the present invention with the same layer thickness as the primarsurfacer layer; it is enough if said stone chip protection layer has athickness between 10 and 20 μm to possess the same mechanical propertiesas the conventional primar surfacer layer. This also means aconsiderable saving of material.

[0069] A further advantage over the prior art is that two instead ofthree booth waste water cycles have to be installed. The recycling ofthe clear coat, e.g. by ultrafiltration, makes it possible to run forthe first time a motorcar standard lacquering which is completely freeof paint sludge. When water borne clear coats are used, it is evenpossible to run the process with only one booth waste water cycle if thecoating efficiency of the water borne clear coat application isoptimized by suitable methods such that the accrued amounts of overspraydo not exceed the demand for the stone chip protection paint of thepresent invention. Besides, the demand for stone chip protection paintcan be controlled by varying the layer thickness, (in particularheightening).

[0070] In case the stone chip protection paint, manufactured accordingto the invention from the concentrated booth waste water, does notexhibit the desired protective properties against mechanical load actingon the overall lacquering from outside, it can be conditioned asspecified in the invention.

[0071] This conditioning is effected by adding the components necessaryfor the desired properties of the stone chip protection layer. It canalso be advantageous to remove the effect pigments, partly orcompletely.

[0072] The object of this conditioning is, in particular, to adjust theadhesion of the stone impact protection layer in such a manner that if astrong mechanical load acts on the overall lacquering from outside,which without the stone chip protection paint of the invention and theuse of a three-layer lacquering (i.e. without primar surfacer layer)would entail a chipping off of the electrocoat, the adhesion to theelectrocoat layer is adapted in such a manner that, on the one hand, thestone chip protection layer is released from the electrocoat layer butthe latter is not torn off therewith from the motorcar body and, on theother hand, the chipping offs are as small as possible. The latter canbe achieved by additives which increase the rebound resilience of thestone chip protection paint to a predetermined degree. The term reboundresilience stands for the property by means of which a mechanicalimpulse (stone impact) is compensated by an elastic deformation. Adamage of the material is thus inhibited.

[0073] The above-mentioned mechanical loads acting on the overalllacquering from outside may involve any kind of mechanical action, suchas, for example, stone impact on motorcar lacquerings, frictionalcontact or impact contact between lacquered articles or any kind ofobjects on laquered surfaces.

[0074] For conditioning the mechanical properties of the stone chipprotection paint of the present invention, binders, such as a watercompatible blocked isocyanate, a melamine resin, a polyurethane resin orpolyester resin; organic solvents, pigments or additives can be used assuitable components.

[0075] These components can be added to the stone chip protection paintalone or in any combination or also as compensation paint having asolids concentration of from 20 to 80% by weight.

[0076] This compensation paint contains all or parts of the componentsnecessary for conditioning the desired mechanical properties of thestone impact-protective layer.

[0077] Thus, a stone chip protection layer cycle is formed according tothe invention, to which base coat overspray and compensation paint areperiodically added.

[0078] Subsequent to the conditioning of the upgraded booth waste wateran equilibrium is established after some time within said cycle whichcan be maintained by the appropriate amount of compensation paint, whichcan be easily determined by the expert.

[0079] The particular advantage in the use of the compensation paintresides in that all components can be added to the stone chip protectionpaint, adapted to the pertinent base coat system, to the correspondingoverspray or to the booth waste water, and that in a single mixingprocedure directly in the spray coating plant or its directneighbourhood. Therefore, the concentrated booth waste water, which cancontain up to 90% water, must not be transported from the lacquerprocessing plant to another place where it is tested in respect of theproperties required for the stone chip protection layer and, if desired,conditioned by the method of the present invention, but all theseprocedures can be done in the same place where the lacquering isconducted.

[0080] The higher the concentration of the compensation paint, the lesswater must be removed from the booth waste water.

[0081] The process of lacquering motorcar bodies comprises applying anelectro-dipcoat primer (CDC), baking the same, applying the stone chipprotection paint of the present invention, drying the same at 50-90° C.,applying a base lacquer, drying the same at 50-100° C., applying a clearcoat and subsequently jointly baking the three lacquer layers at130-160° C.

[0082] The stone chip protection paint of the present invention can beused for lacquering all solid, plane or non-planar smooth or unevenmetallic surfaces which are coated according to the above-specified“base coat/clear coat process” and which are to be protected againstmechanical load outwardly acting on the overall lacquer, said protectionpaint being located between the electrocoat layer and the base coatlayer. Smooth metallic surfaces, such as occur in the lacquering ofplants, apparatuses, windows, in particular motorcars (cars, trucks,bikes etc.) are mainly involved.

[0083] The following examples will illustrate the invention.

EXAMPLES Preparation Example A of a Polyester Resin

[0084] In a reactor provided with stirrer, condenser and heater, as wellas a packed column, 1187 g 1,6-hexanediol and 1473 g dimeric fatty acid(Pripol 1009 of the UNICHEMA company) are weighed and heated such thatthe head temperature of the column does not exceed 100° C. The maximumesterification temperature amounts to 220° C. When the acid number isbelow 5, cooling to 150° C. is effected and 1499 g admerginic acid (anaddition product of linseed oil fatty acid and maleic anhydride,commercial product of the HARBURGER FETTCHEMIE) are weighed. Heating isagain conducted in such a manner that the head temperature of the columndoes not exceed 100° C. The maximum esterification temperature amountsto 220° C. Cooling is effected at an acid number of 38, followed bydilution with 1658 g Butyl glycol. A polyester having a solids contentof 70% and a hydroxyl number of 57 is recovered.

Preparation Example B of a Polyester Resin

[0085] In a reactor provided with stirrer, condenser and heater, as wellas a packed column, 598 g dimethylolcyclohexane, 3098 g dimeric fattyacid (pripol 1009 of the UNICHEMA company) and 371 g dimethylolpropionicacid are weighed and heated in such a manner that the head temperatureof the column does not exceed 100° C. The maximum esterificationtemperature amounts to 220° C. Cooling is effected at an acid number of30, followed by dilution with 1651 g butyl glycol. A polyester having asolids content of 70% and a hydroxyl number of 30 is obtained.

Example 1 (Compensation Paint)

[0086] 337 parts of a polyester resin of preparation example A are mixedwith a blend of 227 parts of fully desalted water and 12 partsdimethylethanol amine with stirring. 39 parts of the commercial melamineresin Luwipal LR 8852 are added thereto with further stirring. The pHvalue is 9.06. The viscosity is adjusted by fully desalted water to 130sec., measured in DIN 4 (German standard) cup.

Example 2 (Compensation Paint)

[0087] 404 parts of the polyester resin of preparation example B aremixed with a blend of 457 parts of totally desalted water and 10 partsdimethylethanol amine with stirring. 47 parts of the commercial melamineresin Luwipal LR 8852 are added thereto with further stirring. The pHvalue is 9.06, The viscosity is adjusted by fully desalted water to 130sec., measured in DIN 4 cup.

Example 3 (Compensation Paint)

[0088] 206 parts of the polyester resin of preparation example B aremixed with stirring with a blend of 289 parts totally desalted water and7.5 parts dimethylethanol amine. 298 parts of the blocked isocyanateBayhydrol LS 2050 of the Bayer AG company Leverkusen are added theretowith further stirring. The pH value is adjusted with an aqueous10%-dimethylethanol amine solution to 8.5. The viscosity is adjusted byfully desalted water to 130 sec., measured in a DIN 4 cup.

Example 4 (Reprocessing of Overspray)

[0089] A laboratory spray booth having a water capacity of 250 literswas filled with fully desalted water. Five different water basecoat-color shades, prepared as described in European patent 502 934,were sprayed with a flow beaker spraying gun. About 2 to 3 kg of eachcolor shade were consumed until the solids content of the boothrecycling water has increased to 1%.

[0090] The so-obtained booth water was upgraded to a solids content of18% by ultrafiltration.

Example 5 (Stone Chip Protection Paint)

[0091] 2 parts of the commercial melamine resin Cymel 327 are added to390 parts of the retentate of the above-described reprocessing withstirring. 268 parts of the compensation paint of example 1 are added tothis blend and the viscosity is adjusted to 35 sec. by fully desaltedwater.

Example 6 (Stone Chip Protection Paint)

[0092] 78 parts of each of the same five water base lacquer-color shadeswhich were used to simulate the overspray (as described in example 4)are mixed with stirring. 268 parts of the compensation paint of example1 is added thereto, likewise with stirring. After adjusting the pH valueto between 9.0 and 9.1, the viscosity is adjusted by fully desaltedwater to 35 sec.

[0093] The stone chip protection paints were sprayed according toconventional methods on phosphated sheet steels coated with a commercialelectro-dipcoat. After a flash off time of 3 minutes, drying wasconducted at three different temperatures. One part of the sheets wasdried for 10 minutes at 100° C., the second part for 10 minutes at 130°C. and the third part for 10 minutes at 105° C. The dry layerthicknesses were between 14 and 19 μm. Thereafter, all sheets wereoverpainted in a conventional manner with commercial water base coat and2 components clear coat comprising mainly isocyanate.

Example 7 (Base Coat with Integrated Stone Impact Protection Paint)

[0094] 100 parts of a metallic base coat with a silver color shade,prepared as described in European Patent 502 934, were blended with 135parts of the compensation paint of example 3 with stirring, and adjustedto a viscosity of 45 sec. (DIN 4).

[0095] The so-modified base coat is sprayed on phosphated sheet steelscoated with a commercial electro-dipcoat and after a flash off time of 5minutes is overpainted with clear coat. The layer thickness of the firstmodified base coat layer was 9 μm and that of the second unmodifiedlayer 7 μm.

[0096] All sheets exhibited a good appearance, comparable toconventional standards.

[0097] The sheets were subjected to a stone impact test, as is common atMercedes Benz AG. To this end, the test sheets were first cooled to −20°C. and were shot with a steel ball having a diameter of 3 mm at a speedof 250 km/h. A penetration up to the sheet should not occur thereby andthe chipping offs should not be greater than 8 mm². All test sheetspassed this test.

1. A water-dilutable stone chip protection paint, comprising oversprayof water soluble base coats and additional binders, pigments, organicsolvents and additives.
 2. The water-dilutable stone chip protectionpaint of claim 1 comprising booth waste water with uncoagulatedoverspray of water soluble base coats.
 3. The water-dilutable stone chipprotection paint of claim 1 or 2 comprising booth waste water upgradedto a solids concentration of from about 10 to 35% by weight, as well asadditional binders, pigments, organic solvents and additives.
 4. Thewater-dilutable stone chip protection paint of any of the precedingclaims containing uncoagulated overspray of water soluble base coats ofdifferent color shades.
 5. The water-dilutable stone chip protectionpaint of any of the preceding claims wherein the additional binder is awater compatible blocked isocyanate, a polyurethane resin, polyesterresin or melamine resin.
 6. The water-dilutable stone chip protectionpaint of any of the preceding claims wherein the solvents being addedare partly or completely miscible with water.
 7. The water-dilutablestone chip protection paint of any of the preceding claims characterizedin that it does not detach itself upon predetermined mechanical load oronly from the electrocoat layer.
 8. The water-dilutable stone chipprotection paint of any of the preceding claims characterized by havinga high rebound resilience.
 9. The water-dilutable stone chip protectionpaint of any of the preceding claims wherein the binder has elastomericproperties after baking.
 10. The water-dilutable stone chip protectionpaint of any of the preceding claims characterized in that it comprisesfrom 20 to 60% by weight binders and from 2 to 10% by weight pigments.11. The water-dilutable stone chip protection paint of claim 10 whereinthe ratio of binders to pigments is between 5:1 and 12:1.
 12. Thewater-dilutable stone chip protection paint of any of the precedingclaims wherein said pigment is an effect pigment, in particular aluminumbronze.
 13. The water-dilutable stone chip protection paint of thepreceding claims wherein said binder is a water compatible blockedisocyanate, a polyurethan, polyester and/or melamine resin.
 14. Thewater-dilutable stone impact protection paint of claim 13 wherein saidpolyester resin has an average molecular weight of from 5,000 to 10,000;exhibits sufficient carboxylic groups which impart to the polyesterresin, after neutralization with bases, sufficient water-dilutablecharacteristics; and contains functional groups, in particular hydroxylgroups, making the polyester resin crosslinkable.
 15. Thewater-dilutable stone chip protection paint of claim 13 or 14, whereinsaid polyester resin has a OH number of from 20 to 80, in particular offrom 30 to 60 and an acid number of from 10 to 50, in particular of from15 to
 35. 16. The water-dilutable stone chip protection paint of claims13 to 15 wherein said polyester resin has a glass transition temperature(Tg) of from −20 to +30° C.
 17. The water-dilutable stone chipprotection paint of any of claims 13 to 16 wherein the polyester is apolycondensation product of a diol and a dicarboxylic acid in thepresence of a component containing more than 2 functional groups
 18. Thewater-dilutable stone chip protection paint of claim 17 wherein the diolis selected from the group consisting of 1,6-hexanediol, neopentylglycol, 1,4-dimethylolcyclohexane, hydroxypivalic neopentyl glycol ester(HPN), perhydrogenated bisphenol A, trimethylolpropane andtrimethylolpropane monoallyl ether.
 19. The water-dilutable stone chipprotection paint of claim 17 or 18 wherein the dicarboxylic acid isselected from the group consisting of adipic acid, phthalic acid,isophthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid ortheir possible anhydrides, in particular from the group of dimeric fattyacids.
 20. The water-dilutable stone chip protection paint of any ofclaims 17 to 19 wherein the component containing more than 2 functionalgroups is a triol, a tricarboxylic acid, a monohydroxydicarboxylic acid,in particular a dihydroxymonocarboxylic acid.
 21. The water-dilutablestone chip protection paint of claim 20 wherein said componentcontaining more than 2 functional groups is trimellithic acid,trimethylolpropane, in particular dimethylolpropionic acid.
 22. Thewater-dilutable stone chip protection paint of any of the precedingclaims additionally comprising organic solvents and additives.
 23. Thewater-dilutable stone chip protection paint of any of the precedingclaims wherein the components to be added to the overspray are addedcompletely or partly in form of a compensation paint.
 24. Thewater-dilutable stone chip protection paint of claim 23 wherein thecompensation paint comprises form 40 to 80% by weight binders.
 25. Thewater-dilutable stone chip protection paint of claim 23 or 24 whereinthe compensation paint additionally comprises up to 20% by weightpigments.
 26. The water-dilutable stone chip protection paint of any ofclaims 23 to 25 wherein the ratio of binders to pigments in thecompensation paint is between 10:1 and 15:1
 27. A process for thepreparation of a water-dilutable stone chip protection paint of any ofclaims 1 to 26 wherein overspray of water soluble base coats resultingfrom the application of the coat by spray painting techniques is used.28. The process of claim 27 wherein uncoagulated overspray of watersoluble base coats is used.
 29. The process of claim 27 or 28 whereinspraybooth waste water is used, concentrated to a solid content of from10 to 35% by weight by removal of water and comprising uncoagulatedoverspray of water soluble base coats.
 30. The process of any of claims27 to 29 wherein overspray of water soluble base coats having differentcolor shades is used.
 31. The process of any of claims 27 to 30comprising adding the necessary components in the form of a compensationpaint having a solid concentration of from 20 to 80% by weight.
 32. Theprocess of claim 31 characterized in that the necessary components arebinders, pigments, organic solvents and additives.
 33. The use of awater-dilutable stone chip protection paint of any of claims 1 to 26 forlacquering motorcar bodies having an electro-dip primer coat, a secondso-called primar surfacer layer and a third layer comprising a watersoluble base coat and a clear coat layer, characterized in that thesurfacer layer is replaced by a stone chip protection layer of the stonechip protection paint of any of claims 1 to 26, said protection layerhaving a thickness of from 10 to 20 μm.
 34. The use of a water-dilutablestone chip protection paint of any of claims 1 to 26 for lacqueringmotorcar bodies having an electro-dip primer coat, a stone chipprotection layer consisting of the stone chip protection paint of any ofclaims 1 to 26 in a thickness of from 10 to 20 μm and a clear coatlayer.
 35. The use of a water-dilutable stone chip protection paint ofany of claims 1 to 26 for preparing a stone chip protection layer ofmotorcar bodies having an electro-dip primer coat, a second so-calledprimar surfacer layer, a third layer comprising a water soluble basecoat and a clear coat layer, characterized in that the surfacer layer isreplaced by a stone chip protection layer of the stone chip protectionpaint of any of claims 1 to 26, said protection layer having a thicknessof from 10 to 20 μm.
 36. The use of a water-dilutable stone chipprotection paint of any of claims 1 to 26 for preparing a stone chipprotection layer of motorcar bodies by applying an electro-dip primercoat (KTL), baking said electro-dip primer coat, applying the stone chipprotection paint of any of claims 1 to 26, drying said stone chipprotection paint at a temperature of from 50 to 90° C., applying a basecoat, drying said base coat at a temperature of from 50 to 100° C.,applying a clear coat, said three layers are baked simultaneously at atemperature of from 130 to 160° C.